Two of Syria's most prominent authors have spoken out against the military actions of the regime. Adonis, widely held as the Arabic-speaking world's greatest living poet, has called the artillery bombardment of the city of Homs "savage" and "horrible", while novelist Khaled Khalifa said the regime was committing "genocide".

"It's savage," Adonis said of the bombardment. "It's the logic of all dictatorships – any dictator would do likewise against the people."

Speaking to the Guardian at an exhibition of his art in London, Adonis reiterated his call for the opposition to use "only peaceful means – like Gandhi", suggesting that "there is no cause which could justify violence", and pointing out that "violence from the opposition gives a justification for the regime to attack."

Nevertheless, the 82-year-old poet was keen to stress that his stance against violence did not indicate any support for the Syrian government, or for undemocratic regimes across the region.

"All Arab regimes, without exception, should fall," he said, "because these regimes incarnate despotism, oppression and obscurantism." The manner of their fall is very important, he continued. "Intervention by foreign powers, particularly military, must be avoided; it is vital that religious fundamentalists don't come to power in the aftermath.

"We must work to found a new Arab society which is secular, plural and democratic."

In an open letter from Damascus, Khalifa, whose novel In Praise of Hatred, shortlisted for the International prize for Arabic Fiction in 2008, is banned in Syria, blamed the "world's blindness" for encouraging "the regime's attempt to eliminate the peaceful revolution in Syria", adding that he wanted to tell people "all over the world … that my people are being subjected to a genocide".

He goes on to describe a "massacre" in the town of Khalidiya, in which "hundreds of thousands of Syrians … took to the streets of their towns and villages … raising their hands in prayer and in tears".

"My people, who faced death with bare chests and songs, are being, in these very moments, subjected to a cleansing campaign," he continued. "Field hospitals are being bombed in cold blood and destroyed … phone lines are cut, and food and medicine are blocked."

He praised the "valour and courage" displayed by Syrian revolutionaries and condemned the world's "silence", which he suggested is complicit "in the murder and extermination of my people".

"I know that writing stands helpless and naked in front of the Russian guns, tanks and missiles bombing cities and civilians," he said, "but I have no wish for your silence to be an accomplice of the killings as well."